1. Field of the Invention
This invention relates to internal combustion engines which have one or more power pistons that reciprocate in one or more cylinders. In particular, the invention relates to engines of this type that operate on a four-stroke cycle in which the power pistons cyclically undergo fuel inlet strokes, compression strokes, expansion strokes and exhaust strokes. More particularly, the invention relates to inlet valves and valve operating components which admit a fuel and air mixture into the cylinders of engines of this type. This invention may be considered an improvement over my prior U.S. Pat. No. 6,672,270, issued Jan. 6, 2004, which is incorporated herein by reference in its entirety.
2. Description of Related Art
Fuel efficiency may be defined as pounds of fuel consumed per horsepower hour of work delivered. The fuel efficiency of most engines of the above identified type varies greatly as a function of power output or engine speed. Efficiency is highest when the engine is operating at or near its full power output and at a steady speed. Efficiency decreases when the engine is operated at reduced power outputs. Many uses of such engines require that power output be reduced much of the time. This is most notably the case with automobile engines. Automobile engines are designed to provide for occasional periods of high power output. This is needed, for example, to accelerate the vehicle on freeway on-ramps or while passing other vehicles or to maintain speed on an upgrade. Power output is reduced when the vehicle is cruising at a steady speed on a freeway or highway or is slowed by traffic conditions. Power output ceases when the vehicle is temporarily stopped with the engine idling.
The practical result of these factors is that most conventional automobile engines operate with reduced fuel efficiency much of the time. This increases operating cost, unproductively consumes fuel resources and has adverse effects on efforts to reduce emission of pollutants into the environment.
This problem arises in part as the typical automobile engine is designed to have a low compression ratio that provides for optimum performance when the engine operates at or near full power output. A higher compression ratio would provide greater efficiency during the periods when the engine is being operated at reduced power output but, in the conventional engine, the high ratio causes overly rapid fuel burning resulting in detonation or “knocking” at times when the engine must be operated at or near maximum power output. Fuel detonation severely strains engine components, creates unacceptable noise and drastically reduces engine efficiency.
It has heretofore been recognized that more efficient overall operation can be realized by designing the engine to have a compression ratio which varies as a function of engine load. Compression ratio can be high when the load is light as detonation is not a problem under that condition. In engines which operate on the Atkinson cycle, a mechanism is provided which varies the length of travel of the power pistons in the cylinders so that the inlet stroke is much shorter than the power or expansion stroke. Some prior engines have auxiliary pistons which reciprocate in chambers that are communicated with the power piston cylinders. Auxiliary piston movement varies the compression ratio in response to changes of engine load. The auxiliary pistons take up a substantial amount of space in the combustion chambers. This requires that the inlet and exhaust valves be smaller than would be desirable for optimum breathing capacity. Engines of these prior kinds require bulky additional components which substantially complicate the engine and which are very prone to rapid wearing.
Although Miller cycle internal combustion engines vary the compression ratio as a function of power output and do not suffer from the drawbacks described above, However, the mode of operation of prior Miller cycle engines requires the effective size of the combustion chamber to be relatively small, resulting in low power output per liter of piston displacement.
The fuel inlet valves and valve operating mechanism of prior Miller cycle engines are not designed to resolve other problems which also adversely affect fuel efficiency. For example, the operator controls the speed and power output of a conventional engine with a throttle valve which is situated in the flow path of the air and fuel. The engine must expend power in order to draw the mixture through the flow path constriction formed by the throttle valve. This throttling loss is a function of the product of the flow rate through the throttle valve and the pressure difference between the upstream and downstream side of the valve. Throttling loss is minimal when the engine operates at maximum power as the pressure difference across the fully open valve is minimal. The throttling loss is also minimal when the engine is operating at or near idling speed as the flow rate through the valve is minimal at that time. Throttle loss rises substantially and may consume as much as 30% of the engine power at the intermediate region of the engines output power range. As has been pointed out above, automobile engines operate within this intermediate power region much of the time. Elimination of the throttle and its attendant losses would substantially increase fuel efficiency of the engine.
A further factor is the increasing use of ethanol as an additive (or significant constituent) to the gasoline fuel. It has been observed that spontaneous detonation of the fuel charge in the combustion chamber, otherwise known as knocking, can result in power loss and even damage to the engine. Although ethanol additives are known to reduce spontaneous detonation, the alcohol has less energy density than gasoline, resulting in reduced power and fuel efficiency. It is very desirable to derive the maximum efficiency from this fuel mixture in order to realize the economy of ethanol-based fuels.